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    Re: Mirages, was: Refraction
    From: Fred Hebard
    Date: 2004 Jul 12, 23:58 -0400

    Trevor,
    
    I am trying to get at the question of objects located on earth, or
    near, rather than stars.  Both of your examples, low and high latitude,
    appear to involve the image being located above its source.  I am
    wonder whether there are any examples of the source of an image being
    on top.  (In the case of light reflected off ice, I would consider the
    point of reflection to be the source).  But I may have a very poor
    understanding of desert mirages.
    
    Fred
    
    On Jul 12, 2004, at 4:44 AM, Trevor J. Kenchington wrote:
    
    > Fred,
    >
    > An image sunk below the horizon could not be seen and thus could not be
    > an image. However, I think what you are getting at is a converse of the
    > classic mirage seen in hot, desert areas.
    >
    > Low-latitude mirages involve light rays bending upwards very near the
    > ground, so that we see light from the sky apparently rising from the
    > ground. But high-latitude mirages involve the reverse bend, so that
    > surface light appears to come from the sky. They are perhaps most
    > common
    > in the form of "ice blink", where sunlight reflected off ice beyond the
    > horizon is visible as a whiteness in the sky. However, there are
    > reports
    > of people seeing, in the sky, inverted images of ships which, in
    > reality, are hull-down over the horizon.
    >
    > I have characterized the two types as "low" and "high" latitude but
    > they
    > are, of course, respectively the result of (1) intense solar heating of
    > a land surface under cooler air and (2) the presence of warmer air
    > overlying a very cold surface.
    >
    >
    > Trevor Kenchington
    >
    >
    > Fred Hebard wrote:
    >
    >> OK ladies & gentlemen.  We have the case of a mirage, where the image
    >> rises above the desert floor.  Are there any counter examples of an
    >> image sinking below the horizon?
    >
    >
    > --
    > Trevor J. Kenchington PhD                         Gadus{at}iStar.ca
    > Gadus Associates,                                 Office(902) 889-9250
    > R.R.#1, Musquodoboit Harbour,                     Fax   (902) 889-9251
    > Nova Scotia  B0J 2L0, CANADA                      Home  (902) 889-3555
    >
    >                     Science Serving the Fisheries
    >                      http://home.istar.ca/~gadus
    >
    
    
    

       
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